Multichannel Systems Roboinject Manual - Manual (Page 72)

Roboinject Manual
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5.2 Clogged Injection Needle
If you observe that your injection needles are frequently blocked, please check the blocked needle
under a microscope to find the cause of the problem.
Injection needle is blocked from outside
DNA / RNA solution flows out of the tip and dries out. The sticky residues will block the tip.
Remove the blockage by moving the needle into fluid for a short moment to dissolve salt crystals,
for example you can move it into the alignment well filled with distilled water (without alignment
tool). If this does not help, you can move the needle right down onto the alignment device so that
the needle actually touches the alignment device. You may also try to cut a little piece from the
tip with a sharp blade.
Possible causes:
? The time lag between alignment, setting the pressure and starting the injection can be too long.
This is especially likely if you are a fresh user and need too much time for the alignment. You
should not need more than about three minutes for the alignment and starting the injection.
Practice the alignment process and the pressure settings with a typical solution without actually
injecting to get used to the procedure.
Injection needle is blocked from inside
Particles in the RNA / DNA sample can clog the needle. The vertical alignment of the needle makes
clogging more likely if particles are present than the angular direction of the needle in a manual
injection setup.
Possible causes:
? Can you see particles under the microscope? There may be residues from the DNA / RNA
preparation, for example PCR beads, particles from a column, remains of an agarose gel or
extraction kit, and so on. There may also be cell debris, if the DNA is extracted from bacteria.
? If you cannot see any possible cause, check your RNA / DNA solution. Maybe the concentration is
too high, or there is too much salt, too much protein, or too much cell debris in the preparation?
Centrifuge the sample longer or more intensely (for example for 5 min at 2000 g or for 1 min
at 6000 g) to remove any particles immediately before loading the needle. Take up the solution
carefully from the top, not touching the well bottom with the pipette tip. Prepare the RNA / DNA
sample more carefully next time and control the purity according to standard molecular biology
protocols.
? The pipette tips (Microloader) you are using to fill the injection needle with oil may be
contaminated. For example, if the tip rack has been opened for too long, the tips can get dusty.
Use a rack with new clean pipette tips.
? The injection needles may be contaminated. If the unit has been opened for too long, dust can
deposit in and on the needles.
Use a new unit of injection needles.